E-Poster Presentation ESA-SRB-ANZBMS 2021

BIOMECHANICAL DETERMINANTS OF JAW FRACTURE AND REPAIR   (#715)

Olga Panagiotopoulou 1 , Hyab Mehari Abraha 1 , Pranav Haravu 2 , Michelle Shang 2 , Jose Iriarte Diaz 3 , Russell R Reid 2 , Callum F Ross 4
  1. Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia
  2. Department of Surgery, Section of Plastic Surgery, The University of Chicago Medical Centre, Chicago, Illinois, USA
  3. Department of Biology, The University of the South, Sewanee, Tennessee, USA
  4. Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois, USA

Choosing the best technique to fix a broken jaw is an important topic in oral and maxillofacial surgery and there is ongoing debate amongst surgeons about whether non-rigid or rigid fixation is the best method of treatment1-5. We have some understanding of the mechanics of the healthy mandible during feeding6-10, and the impact of fracture fixation technique on static bite forces11-14, but we do not know how treatment rigidity alters bone strain regimes during chewing. Hence not only do we not know which fixation treatment results in better healing, we do not have a body of biomechanical theory to explain why one treatment modality is better. Knowledge of the abnormal strain environments —strain regimes to which bones are not adapted— in and around the fracture zone and implants is important if, abnormal strain environments can stimulate post-operative complications such as sub-optimal bone (re)modelling, resulting in weak bone morphology, slow healing, and mal-unions15.

This study is the first to use realistic simulations to compare the biomechanical behaviour of the human and macaque mandibles pre and post angle fracture and fixation. We show that macaques are ideal animal models for oral and maxillofacial research because they chew like humans. We also show that non-rigid fixation results in higher strains in the bone-implant interfaces and a higher degree of interfragmentary displacement than rigid fixation (Figure1). One of the most salient results of our study is the importance of laterality of chewing behaviour post treatment. Chewing contralateral to the fracture increases interfragmentary displacement beyond the optimal threshold suggested by orthopaedic literature (Figure1). This shows that non-rigid fixation and contralateral chewing likely inhibit bone healing and accelerate post-operative complications. Future research combining in vivo experiments, biomechanical modelling and histology will further elucidate the links between treatment rigidity and bone healing in the mandible.

 

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